Intravaginal devices such as diaphragms and other cervical barrier devices are useful for contraception and disease prevention. Such devices can also be used for collecting menstrual discharge, collection of vaginal samples, or to deliver therapies. A typical design of an intravaginal device consists of a flexible rim surrounding a hemispheric-shaped dome, often manufactured using a mold that simultaneously forms both the rim and the dome. The dome provides barrier, collection, and/or drug delivery functions, whereas the rim holds and supports the dome during insertion and during wear within the vagina.
Various designs and methods of construction are known. One of the most common designs includes a metal spring in the rim of the device to provide elastic force that restores the rim to its expanded configuration after being compressed during vaginal insertion. The spring is incorporated into the rim by a molding process that simultaneously creates the dome and covers the spring with a continuous and unbroken layer of elastomer. Other designs use rims that are entirely elastomeric without metal springs. Although molding the rim and dome as a single piece creates devices with smooth surfaces that provide comfort in use, the domes created by this method are relatively thick. This is because it is difficult to mold parts having a relatively large surface area as a thin piece. The dome portion must remain relatively thick to allow proper filling of the mold because the injected polymer must flow a long distance through a narrow mold cavity.
It is advantageous, however, for an intravaginal device to have a thin dome. Thin domes are compact when compressed for insertion, and they can be made very soft and compliant. To create a thin dome requires methods that employ assembly of the device from separate dome and rim pieces. The film piece is attached to the rim where it can be further shaped and expanded by thermoforming (softening by heating, and drawing by vacuum into a mold shaped to the desired final dome shape), which further reduces the dome thickness. In addition, the device assembled from separate pieces allows a single rim design to be used with multiple different dome shapes such as the roughly hemispheric shape of conventional diaphragms, or other dome shapes.
A significant disadvantage of diaphragms and similar devices assembled from a separate dome piece and a separate rim piece that has not been recognized or overcome in the prior art is the exposure of an unprotected and potentially harsh outer edge of the dome material upon attaching the dome to the rim. FIG. 1, for example, illustrates a common rim design in the prior art having a circular cross-section with a width 18 less than or equal to its height 20. As illustrated in FIG. 1, the dome piece 10 is positioned for attachment at a typical attachment site 16 on the upper surface of the rim 12. When attached, the dome piece edge 14 is disadvantageously exposed and unprotected.
A sharp edge may be created at an outer edge of a dome piece if the dome film is cut to shape before attachment. A rough or sharp edge just outside the attachment site can also be created with a known alternative assembly method of simultaneously attaching a plurality of domes to the top of a plurality of rims, employing a multi-headed welding tool. An oversized uncut piece of dome film is stretched over the multi-headed welding tool. The multi-headed welding tool presses through the sheet of dome film onto the rims, and the web of film outside the perimeter of the welding tool softens to form a weld line. The waste web is subsequently pulled free from the heat-softened weld line. Although precautions can be taken during manufacture to reduce roughness of the exposed edge, for example, by adding subsequent smoothing steps or shaping the welding tool to minimize residual roughness, these extra steps add cost and complexity, and may be only partially effective.
The outer edge of the attached film may be sufficiently rough or sharp to irritate or injure the vagina during insertion or wear, and irritate or injure the penis during sexual intercourse. Even if the weld-edge roughness is sufficiently minimal that detectable injury does not result, any roughness felt during insertion, wear or intercourse is disadvantageous.
Another disadvantage of attaching the dome to an unprotected surface of the rim is the resulting exposure of the edge of the dome to forces that may pull it loose from the rim. During insertion or with movement during wear, an exposed edge of the dome material may rub against epithelial surfaces, and, with sufficient purchase of the epithelium on the edge, may be pulled loose from the rim, especially if a local weakness in the attachment bond is present. Movement during intercourse may also contribute to detachment of the dome material due to traction on an exposed dome edge. Any detachment along the attachment bond or any separation of the dome material from the rim can compromise barrier function of the device. Even partial detachment that does not compromise the barrier function can create a crevice or flap between the dome and rim that is difficult to clean and reduces the suitability of the device to function as a re-usable device.
Also, diaphragms and similar devices may be difficult to grasp for positioning within or removal from the vagina. To remove a typical diaphragm, a user must grasp the device at the rim, generally by pushing the dome material up inside the perimeter of the rim to allow the fingertip to curve around the top of the rim from the inside, and then by pulling the rim downward and out of the vagina. Grasping the upper surface of the rim can be difficult since the dome material tends to interfere with access to this portion of the rim, and since the grasping finger must traverse the entire height of the rim to gain purchase on its upper surface.